Conventionally, as a rotor used in a motor, a rotor having a Lundell structure with a so-called permanent magnet field disclosed in Japanese Patent Laid-Open Publication No. 2012-115085 and Japanese Utility Model Laid-Open Publication No. 5-43749 is known. Such a rotor includes two rotor cores combined with each other and a field magnet arranged between the two rotor cores. Each of the rotor cores has a plurality of claw-shaped magnetic poles aligned in a peripheral direction. The field magnet causes the claw-shaped magnetic poles to function as alternately different magnetic poles.
Moreover, in the rotor disclosed in Japanese Patent Laid-Open Publication No. 2012-115085, in order to increase an output of the motor, a back-surface magnet for rectifying a magnetic path is arranged on a back surface of the claw-shaped magnetic pole. Moreover, in this rotor, in order to increase the output of the motor, an inter-pole magnet for rectifying the magnetic path is arranged between the alternately arranged claw-shaped magnetic poles. Such a motor is accommodated in a case having a yoke housing having a cylindrical shape with a bottom and an end frame provided on one end of the yoke housing.
In the motor as above, the yoke housing which is a magnetic body is located on one end surface side in an axial direction of the rotor, and the end frame made of a resin is located on the other end surface side in the axial direction of the rotor. In this case, a part of a magnetic flux from the field magnet of the rotor leaks to the case (yoke housing), and there is a concern that a magnetic flux amount (magnetic balance) is unbalanced between the N-pole and the S-pole. Moreover, in this case, detent torque becomes unbalanced, and there is a concern that it causes deterioration of sound and vibration. Furthermore, in this case, a part of the magnetic flux from the field magnet of the rotor leaks to the case (yoke housing) and there is a concern that it causes deterioration of output characteristics.